What are Enzymes?
Enzymes are biological molecules (usual proteins) that dramatically accelerate the rates of nearly all chemical processes that occur within cells. So, enzymes are biological catalysts. Enzymes are highly selective catalysts, which means that each enzyme only accelerates one type of reaction. Enzymes are necessary for digestion, liver function, and many other things. Too much or too little of a specific enzyme can be harmful to one's health.
Substrates are the molecules with which an enzyme interacts. The substrates attach to an area of the enzyme known as the active site. The enzyme and the substrate must fit together to work. The enzyme-substrate interaction is explained by two theories. The active site of an enzyme is precisely shaped in the lock-and-key model to hold specific substrates. The active site and substrate do not fit perfectly together in the induced-fit model; instead, they both change shape to connect.
Parts Of Enzymes
An apoenzyme is the protein component of an enzyme. Apoenzymes lack prosthetic groups thus they are incomplete and are in an inactive form.
A Cofactor is the non-protein component of an enzyme. It is a non-protein chemical compound or metallic ion that is required for the activity of an enzyme.
A holoenzyme is formed when an apoenzyme and a cofactor combine to form a holoenzyme. Aminotransferase + pyridoxal phosphate is one such example.
Examples
• DNA polymerase and RNA polymerase are two common examples of holoenzymes.
• Trypsin, pepsin, and urease are examples of apoenzymes.
• Cofactors can be either organic or inorganic.
Coenzymes include nicotinamide adenine dinucleotide (NAD) and ascorbic acid.
A cofactor is a non-protein chemical compound that is required for the protein’s biological activity. Many enzymes require cofactors to function properly.
Classes of enzymes
Following are 6 main classes of enzymes
1-Oxidoreductases
Oxidoreductase is an enzyme that catalyzes the oxidation reaction in which electrons tend to move from one form of a molecule to the other. These enzymes catalyze oxidation and reduction reactions, such as pyruvate dehydrogenase, which catalyzes pyruvate oxidation to acetyl coenzyme A.
2-Transferases
Transferase’s enzymes aid in the movement of functional groups between acceptor and donor molecules. These catalyze the transfer of a chemical group from one compound to another. A transaminase, for example, transfers an amino group from one molecule to another.
3-Hydrolases
Hydrolases are hydrolytic enzymes that catalyze the hydrolysis reaction by cleaving the bond and hydrolyzing it. They catalyze a bond's hydrolysis. Pepsin, for example, hydrolyzes peptide bonds in proteins.
4-Lyases
Lyases Add water, co2, or ammonia across double bonds, or removes these to form double bonds. These catalyze the breakage of bonds without catalysis, e.g. aldolase (an enzyme in glycolysis) catalyzes the splitting of fructose-1, 6-bisphosphate to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate.
5-Isomerases
The Isomerases enzymes catalyze the structural shifts present in a molecule, thus causing the change in the shape of the molecule. They catalyze the formation of an isomer of a compound. Example: phosphoglucomutase catalyzes the conversion of glucose-1-phosphate to 4 glucose-6-phosphate (phosphate group is transferred from one to another position in the same compound) in glycogenolysis (glycogen is converted to glucose for energy to be released quickly).
6-Ligases
The Ligases enzymes are known to charge the catalysis of a ligation process. Ligases catalyze the association of two molecules. For example, DNA ligase catalyzes the joining of two fragments of DNA by forming a phosphodiester bond.
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